Taipan 15 rear exhaust
Yes, not a current production engine (circa 1972) but still a very cool looking engine.
Home brew fuel: 70% methanol, 10% nitro & 20% castor oil = RPM 16,680 on an APC 7 x 4 prop
Not bad for a 36 year old engine I found in a pawn store for $25 [8D]